Re: [PATCH v2] mtd: rawnand: marvell: check for RDY bits after enabling the IRQ

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Mon, 1 Oct 2018 22:15:28 +0000
Chris Packham <Chris.Packham@alliedtelesis.co.nz> wrote:

> On 02/10/18 11:13, Boris Brezillon wrote:
> > On Mon, 1 Oct 2018 22:01:27 +0000
> > Chris Packham <Chris.Packham@alliedtelesis.co.nz> wrote:
> >   
> >> On 02/10/18 10:41, Boris Brezillon wrote:  
> >>> On Mon, 1 Oct 2018 22:34:38 +0200
> >>> Boris Brezillon <boris.brezillon@bootlin.com> wrote:
> >>>         
> >>>>>
> >>>>> I'd previously tried readl() based on the same hunch. No change.
> >>>>>
> >>>>> I think my snippet above might be misleading. While a delay between
> >>>>> readl_relaxed() and the if should not change the outcome, this is also a
> >>>>> delay between marvell_nfc_enable_int() and marvell_nfc_disable_int()
> >>>>> which is probably more significant. Sure enough if I move the delay to
> >>>>> just before the marvell_nfc_disable_int() the error is not seen.  
> >>>>
> >>>> AFAICT, your timeout always happens when waiting for RDREQ, not RDYM.
> >>>> So maybe disabling MRDY too early has a side-effect on the RDREQ event.  
> >>>
> >>> Can you try with this patch [1]? It should ensure that NDSR_RDY bits
> >>> are cleared before starting an operation.
> >>>
> >>> [1]http://code.bulix.org/lgs30c-468205
> >>>      
> >>
> >> No luck. I applied that on top of Daniel's and got the same result.
> >>
> >> One thing that does look promising is the following modification of
> >> Daniel's patch[1]. Which moves the RDY check to before where the
> >> interrupts are enabled.  
> > 
> > Except we still don't know why this is happening, and I'm not sure I
> > want to take a fix without understanding why it does fix the problem.  
> 
> Agreed. My only guess is that there is some interrupt that is missed in 
> the short period they are disabled when calling complete().

Disabling interrupts when taking a spinlock means masking the IRQ line,
but the interrupt still exists and should be there when linux unmasks
the IRQ line. I don't think this is the problem we're chasing.

Looks more like something 

> 
> > Also, it looks like complete() is not called until the RDDREQ, WRDREQ
> > and WRCMDREQ are cleared in the interrupt handler [1], which is weird.
> > Miquel, do you happen to remember why you had to do that?
> > 
> > [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mtd/nand/raw/marvell_nand.c?h=v4.19-rc6#n689
> >   
>